RSS Feed Print
The False Alzheimer's Diagnosis
Myriam
Posted: Tuesday, August 28, 2012 6:54 PM
Joined: 12/6/2011
Posts: 3326


From Alzheimer's Daily News:


(Source: Wall Street Journal) - More than 100 other conditions, from vitamin and hormone deficiencies to rare brain disorders, can mimic Alzheimer's disease, experts say. Some are readily treatable.


Alzheimer's symptoms such as confusion, memory loss and personality changes also can be side effects from medication. In many cases, the cognitive symptoms vanish when medication is stopped.

 

It isn't just primary-care physicians who may miss underlying conditions. "Every Alzheimer's expert living today has been fooled," said P. Murali Doraiswamy, chief of biological psychiatry at Duke University Medical Center.

 

Autopsy studies of nearly 1,000 dementia patients at 30 top centers supported by the National Institute on Aging from 2005 to 2010 found that between 17% and 30% of those diagnosed with Alzheimer's disease had been misdiagnosed and had other conditions.

 

Traditionally, Alzheimer's disease, whose main symptoms include memory loss, confusion and changes in personality or mood, could only be definitively diagnosed when an autopsy revealed the telltale amyloid plaques and tangles in the brain. But a new form of PET scan can spot such amyloid buildup in the living.

A positive test can't confirm Alzheimer's, because some people have amyloid plaques and never develop Alzheimer's. But a negative PET scan can rule out Alzheimer's and spur physicians to search for other explanations.

 

Go to full story: http://online.wsj.com/article


Zen
Posted: Thursday, August 30, 2012 12:45 AM
Joined: 7/14/2012
Posts: 55


The only problem is, they're not sure what the role/function/etiology is of the plaques they're talking about.  20% of healthy, functioning older adults, with no symptoms of Alzheimer's, have the plaques; and some people who have symptoms of Alzheimer's with no other known explanation don't have the plaques (or at least not in the amount expected).

 

Removing the plaques doesn't "cure" or even slow down the disease process, either.  So finding them doesn't mean you had Alzheimer's, and not finding them doesn't mean you don't.

 

They just don't know enough about what's going on to pin all hopes on one test of questionable value, and which has an 18% false negative rate on top of it all.  There is also a rate of 5% false positives - people whose test results come back positive when they don't really have Alzheimer's.

 

Plus, as people who fear they MIGHT have Alzheimer's push for the test, the rate of false positives is BOUND to go up - that 5% false positive rate is for people who are showing signs/symptoms of Alzheimer's.  When people start pushing to have the test who are otherwise healthy, that 20% of healthy older adults who have the plaques but don't have Alzheimer's will start getting tagged as halving Alzheimer's when they don't.  That'll raise the number of false positives a LOT.

 

Even Eli Lily admits that a positive result from this test DOES NOT mean you have Alzheimer's - so what use is the test, other than to confirm a diagnosis?  But it should not be allowed to reject a diagnosis if it comes back negative because of the 18% false negative rate.

 

I think the best diagnostic methods are still to monitor functioning and behavior.  We don't really know what those plaques are to start with.  They do seem to be correlated to Alzheimer's, but there is no evidence they're a cause - in fact there's quite a bit of evidence that they are NOT a cause, and not even necessarily a symptom. 

 

 Correlation is not the same as causation, and even a strong correlations doesn't mean something ALWAYS happens.

 

For instance, we all know there's a VERY strong correlation between smoking and lung cancer; yet not every one who smokes gets cancer, and not all lung cancer is caused by smoking.  So all we really know is that a LOT of people who smoke get lung cancer.

 

Similarly, there's a correlation between those plaques and Alzheimer's; but not everyone who has them has Alzheimer's, and not everyone who has Alzheimer's has the plaques.  All we really know is that a lot of people who have the plaques also have Alzheimer's; but not everybody.


Daisy1
Posted: Tuesday, October 2, 2012 3:44 PM
Joined: 9/19/2012
Posts: 1


Please have your blood checked for iron deficiency!
Mimi S.
Posted: Tuesday, October 2, 2012 3:49 PM
Joined: 11/29/2011
Posts: 7027


Daisy, 

You responded to a post from last August. 


That's something I had to learn: to check the date it was posted.


And welcome to our boards.


Do tell us more about yourself.